Pipe heating arrangement



N v- 1967 w. c. KAHN 3,354,292

P IPE HEAT ING ARRANGEMENT Original Filed July 16, 1963 INVENTOR 4441.76 6 KA/VA/ United States Patent 3,354,292 PIPE HEATING ARRANGEMENT Walter C. Kahn, Westport, Conn., assignor to Electro-Trace Corporation, Danbury, Conn. Original application July 26, 1963, Ser. No. 297,875. Divided and this application June 19, 1967, Ser. No. 647,070

7 Claims. (Cl. 219-301) ABSTRACT OF THE DISCLOSURE A pipe heating arrangement comprising, in combination, current conductive pipe means having a plurality of "communicating sections and containing a fluid, at least one of the sections comprising a plurality of discrete portions communicating with one another; a plurality of thin flat elongated heating strips each including a thin resistance element, a pair of elongated electrodes electrically connected with the resistance element so that current flows transversely through the resistance element across the length of the same, electrical insulating means surrounding and substantially coextensive with the resistance element and electrodes, and connector means at the ends of the strip and having terminals connected with the electrodes, respectively, the strips being respectively disposed on the outer surfaces of the sections and the portions extending along the length of the same with the electrical insulating means insulating the heating strips from the sections and portions, and the connector means being respectively located at each end of at least one of the communicating sections and the portions; jumper wire means connecting the connector means at one end of at least one other section, anda single jumper wire connecting the connector means at one end of one portion to the connector means at'one end of an adjoining portion; switching means connected to the connector means at the other end of the one section and the one portion and adapted to be connected to a voltage source; and thermal insulating means surrounding the pipe means and the heating strips for minimizing heat radiation to the ambient atmosphere.

Cross reference to related applications This application is a division of my copending application, entitled Pipe Heating Arrangement, Serial No. 297,875, filed on July 26, 1963.

Background 0) the invention The present invention relates to a pipe heating arrangement, and more particularly to an arrangement for heating pipes through which a fluid or liquid flows so that the fluid is maintained at a desired temperature, or freezing of a liquid in a pipe is prevented.

It is known to provide electric heating elements on pipes, and more particularly on pipes enveloped in a thermal insulating material. However, the arrangements of the prior art have the disadvantage that narrow heating elements disposed between the pipe and the insulating material, create longitudinal air gaps between the pipe and the insulating material. Furthermore, it is necessary to connect a heating element which has terminals at the ends thereof at both ends of the pipe to a source of voltage, so that access to both pipe ends, and to both ends of the heating element is necessary.

These disadvantages have been overcome with the arrangement disclosed in my above-mentioned copending application. However, other problems still exist in connection with such pipe heating arrangements. Specifically,

it is often not possible to provide the elongated heating element which is disclosed in my copending application, in the form of a single unitary strip. This is particularly true of branch pipe systems, where a main pipe consists of a plurality of discrete sections which are longitudinally arranged and joined by pipe connectors, with branch pipes being similarly joined to these pipe connectors and extending at an angle to the main pipe. If, now, the heating element had to be provided in form of individual strip portions each of which was to be used on one pipe section or branch pipe, then it was heretofore necessary to provide a separate electrical connection for each of these portionsnecessitating free access to each pipe section or branch pipe. This greatly limits the range of applicability of pipe heating arrangements because the necessary relatively cumbersome installations are expensive, and because very frequently there is simply no possibility of gaining access to all pipe portions and branch pipes to make or maintain the required electrical connections.

Summary of the invention The present invention overcomes the disadvantages of the prior art.

More particularly, the present invention provides a pipe heating arrangement in which only one point of an entire pipe system comprising pipe sections and branch pipes, need be accessible for connecting heating elements extending along the pipes, to switching means or to a source of voltage.

Briefly stated, one feature of my invention resides in the provision of a pipe heating arrangement in which a thin flat heating strip is used for heating a pipe arrangement containing a fluid and comprising a number of pipe sections and for branch pipes. This heating strip, including a thin resistance element, a pair of elongated electrodes electrically connected with said heating element, and connector means at one end of the strip and having terminals connected with the electrodes, is placed on the outer surface of these sections and/ or branch pipes, and attached to the same to extend along their entire respective length.

The main connector means may be located at the end of the pipe arrangement, or at the particularly accessible point of the pipe arrangement, so that the source of voltage has to be connected only to one point of the arrangement to which access is easily possible.

Auxiliary connector means may be provided at both ends of the heating strips of selected pipe sections and/or branch pipes, and jumper wires may be provided for connecting the auxiliary connectors or heating strips on different pipe sections and/or branch pipes. However, only one main connector at one point of one pipe section has to be connected to the voltage source.

The switching means of the heating element-which latter of course consists of a plurality of discrete elements connected by the aforementioned jumper Wires-is preferably controlled by a thermal sensor, such as a thermostat. It is to be understood that, while the term thermostat" is used hereafter for convenience, it is intended to encompass all types of thermal sensors, and also that the provision of such a sensor is not mandatory.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.

Brief description of the drawing Description of the preferred embodiments Referring now to the drawing, and more particularly to FIG. 1, a pipe 1 is enveloped by a thermal insulating material 2 provided with a cutout 2a which may be located at the end of the insulated pipe.

A thin flat elongated heating strip 3 is disposed on the outer surface of pipe 1 within the insulating material 2.

Heating strip 3 has two outer layers of an insulating material, for example of the trademarked materials Teflon or Aclar, heat bonded to each other and to a glassasbestos layer which is sandwiched between the outer layers and protected by the same from heat and moisture. A conductive resistance layer 3a is embedded in the glassasbestos fiber layer. A voltage applied to electrodes 3b causes a current to flow transversely to the elongation of the strip across the resistance element 3a. Consequently, the same heat per unit of area regardless of the length of the strip is produced when current flows through the resistance element 3a. Heating strips of this type but without the Teflon or Aclar cover are known, and are not an object of the present invention. U.S. Patents 2,952,761, 2,803,566 and 3,002,862 disclose related subject matter.

A connector means 4 is provided at the end of strip 3 and includes a flexible bag-shaped insulating end piece 4a to which a threaded connector piece 4b is attached into which wires 7, 7' are inserted. A pair of wires 7a is connected to the ends of a wire 7, and a pair of wires 7a is connected to the wire 7. Wires 7a, 7a are connected'to the respective electrode 3b. When a voltage source is connected to wire 7, current flows through the electrodes 3b, and across the heating element 3a.

Annular straps S embrace pipe 1 and heating strip 3 to hold the same in place. The width of heating strip 3 is, for example, 3 which is less than the circumference of pipe 1, so that the insulating material 2 is in direct contact with the greater part of the outer surface of pipe 1, particularly since the heating strip is very thin, for example less than Therefore, the usual oversize insulation is not required, and there are no inefiicient air spaces between the insulating material 2 and the pipe 1. Tracer pipes or heating cables, and the cost of labor and material for bonding the tracers to the pipe are eliminated.

Since the heat output is spread evenly over a three inch wide surface, the heat density is low, for example 1 1 watt per square inch, eliminating coking or spoilage due to-overheating or particularly hot spots. After a shutdown, the heat is gradually increased so that the temperature of a fluid in the pipe is restored without harm to even the most sensitive fluids. 1

The Teflon or Aclar insulation of the strip has the advantage that it is completely unaifected by weather, corrosive atmosphere, condensate, oils and industrial acids and caustics, and that the material absorbs no water. Due

to these properties of the insulating layers of the heating strip, the same is practically unaffected by time.

- Due to the fact that the source of voltage need be connected only to one end of the strip, any length of pipe can be heated by a correspondingly long strip attached thereto, while only the portion of the pipe where the connector 4 is located, must be disposed to be accessible for service and repair. Access is facilitated by the cutout 2a in the insulating material 2, and as shown in FIG. 1, a

, thinner layer of insulating material 2b is placed in cutout 2a and hassuch a thickness that the connector part 4b projects above insulating layer 2b. Since the electrical connec ions in the region of connector 4 produce addi- 4 tional heat, a thinner thermo-insulating layer 2b is sufiicient.

The construction illustrated thus far is essentially like that known from my copending application, Serial No. 297,875, and has been included to facilitate an understanding of the invention.

FIG. 2 illustrates an embodiment in accordance with the present invention in a simplified manner, omitting the insulating material 2 for the sake of clarity. I

As shown in FIG. 2, two pipe sections 11a and 11b are separated by a valve 10. A by pass section 11c connects pipe sections 11a and 11b. Pipe section 11a has a heating strip 13a secured thereto by straps, not shown, and a connector means 14a at one end of strip 13a is connected by a wire 20a to a source of voltage, not shown. Wire means 14b corresponds to wire 7 in FIG. 1, and comprises two wires connected to the'electrodes of the heating strip.

A thermostat bulb 6, also shown in FIG. 1, is connected by a thermostat capillary 6a to thermostat 21 which is electrically connected with switching means 20 and controls the same. When the temperature sensedby thermostat bulb 6 exceeds a selected temperature, thermostat 21 causes disconnection of the switch means 20 so that no current flows through wire means 14b to connec'tor means 14a.

Heating strips are placed on the three sections of by-pass pipe 110, and each strip 130' has connector means at the ends thereof which are connected to each other by jumper wires 14d. One connector means 14c is connected by a jumper wire 14c to the connector means 14] at the other end of heating strip 13a. The connector means 14h at one end of heating strip 13b is also connected by a jumper wire to the connector means 14g at the end of the by-pass pipe 110. Only one wire, corresponding to wire 7 in FIG. 1, has to be inserted into each'connector means.

Although all pipe sections are uniformly heated by the heating strips, only connector means 141: has to be connected to the switching means 20, and only one jumper wire is-needed to correct any two heating strips.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of pipe heating arrangements diflering from the types described above.

While the invention has been illustrated and described as embodied in a pipe heating arrangement incorporating electric heating elements through which the current flows across the length of the heating element and the pipe, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning'and range of equivalence of the following claims.

What is new and desired to be secured by Letters Patent is set forth in the following:

1. A pipe heating arrangement comprising, in combination, current conductive pipe means having a plurality of communicating sections and containing a fluid, at least one of the sections comprising a plurality of discrete portions communicating with one another; a plurality of thin flat elongated heating strips each including a thin resistance element, a pair of elongated electrodes electrically connected with said resistance element so that current flows transversely through said resistance element across the length of they same, electrical insulating means surrounding and substantially coextensive with said resistance element and electrodes, and connector means at the ends of said strips and having terminals connected with said electrodes, respectively, said strips being respectively disposed on the outer surfaces of said sections and said portions extending along the length of the same with said electrical insulating means insulating said heating strips from said sections and portions, and said connector means being respectively located at each end of at least one of said communicating sections and said portions; jumper wire means connecting the connector means at one end of said one section with the connector means at one end of at least one other section, and a single jumper wire connecting the connector means at one end of one jumper wire connecting the connector means at one end of one portion to the connector means at one end of an adjoining portion; switching means connected to said connector means at the other end of said one section and said one portion and adapted to be connected to a voltage source; and thermal insulating means surrounding said pipe means and said heating strips for minimizing heat radiation to the ambient atmosphere.

2. A pipe heating arrangement as defined in claim 1, wherein said pipe means is constituted of metallic material.

3. A pipe heating arrangement as defined in claim 1; and further comprising temperature-responsive means operative for responding to the temperature of fluid in said pipe means and operatively connected with said switching means for controlling the same.

4. A pipe heating arrangement as defined in claim 3, wherein said temperature-responsive means comprise thermostat means.

5. A pipe heating arrangement as defined in claim 4, wherein said thermostat means is at least partially disposed inwardly of said thermal insulating means.

6. A pipe heating arrangement as defined in claim 1, wherein said strips each have a width less than the circumference of said pipe means.

7. A pipe heating arrangement as defined in claim 1, wherein the diameter of said one portion differs from the diameter of the remaining portions.

References Cited UNITED STATES PATENTS 2,274,839 3/1942 Marick 219-301 X 2,519,920 8/1950 Miner 2l9-301 2,686,109 8/1954 Moule 219301 X 3,120,600 2/1964 True 2.19538 X FOREIGN PATENTS 527,759 10/ 1940 Great Britain.

RICHARD M. WOOD, Primary Examiner. C. L. ALBRITION, Assistant Examiner. 

1. A PIPE HEATING ARRANGEMENT COMPRISING, IN COMBINATION, CURRENT CONDUCTIVE PIPE MEANS HAVING A PLURALITY OF COMMUNICATING SECTIONS AND CONTAINING A FLUID, AT LEAST ONE OF THE SECTIONS COMPRISING A PLURALITY OF DISCRETE PORTIONS COMMUNICATING WITH ONE ANOTHER; A PLURALITY OF THIN FLAT ELONGATED HEATING STRIPS EACH INCLUDING A THIN RESISTANCE ELEMENT, A PAIR OF ELONGATED ELECTRODES ELECTRICALLY CONNECTED WITH SAID RESISTANCE ELEMENT SO THAT CURRENT FLOWS TRANSVERSELY THROUGH SAID RESISTANCE ELEMENT ACROSS THE LENGTH OF THE SAME, ELECTRICAL INSULATING MEANS SURROUNDING AND SUBSTANTIALLY COEXTENSIVE WITH SAID RESISTANCE ELEMENT AND ELECTRODES, AND CONNECTOR MEANS AT THE ENDS OF SAID STRIPS AND HAVING TERMINALS CONNECTED WITH SAID ELECTRODES, RESPECTIVELY, SAID STRIPS BEING RESPECTIVELY DISPOSED ON THE OUTER SURFACES OF SAID SECTIONS AND SAID PORTIONS EXTENDING ALONG THE LENGTH OF THE SAME WITH SAID ELECTRICAL INSULATING MEANS INSULATING SAID HEATING STRIPS FROM SAID SECTIONS AND PORTIONS, AND SAID CONNECTOR MEANS BEING RESPECTIVELY LOCATED AT EACH END OF AT LEAST ONE OF SAID COMMUNICATING SECTIONS AND SAID PORTIONS; JUMPER WIRE MEANS CONNECTING THE CONNECTOR MEANS AT ONE END OF SAID ONE SECTION WITH THE CONNECTOR MEANS AT ONE END OF AT LEAST ON OTHER SECTION, AND A SINGLE JUMPER WIRE CONNECTING THE CONNECTOR MEANS AT ONE END OF ONE JUMPER WIRE CONNECTING THE CONNECTOR MEANS AT ONE END OF ONE PORTION TO THE CONNECTOR MEANS AT ONE END OF AN ADJOINING PORTION; SWITCHING MEANS CONNECTED TO SAID CONNECTOR MEANS AT THE OTHER END OF SAID ONE SECTION AND SAID ONE PORTION AND ADAPTED TO BE CONNECTED TO A VOLTAGE SOURCE; AND THERMAL INSULATING MEANS SURROUNDING SAID PIPE MEANS AND SAID HEATING STRIPS FOR MINIMIZING HEAD RADIATION TO THE AMBIENT ATMOSPHERE. 